The present invention relates to the construction of solar collectors and in particular to a solar collector having a central core through which fluid flows to be heated by the rays of the sun.
Early solar collectors were known to employ a reflecting wall, generally curved to gather and force sunlight onto a central conduit through which a fluid media passes. The collectors are quite long and wide while the central conduit, or fluid core, is generally very small so that much sunlight can be concentrated on a very small quantity of fluid media in the hope of transferring a maximum amount of energy to the flowing media. Such collectors, however, did not optimize energy transfer; were too large for economical production or installation; and, above all, failed to allow for sufficiently high flow rates desired in most applications.
Various attempts were made to improve the design, i.e., parameters of curvature and size, of the reflecting wall as well as in the shape and cross-sections of the central core. For example, in SCHOOK, U.S. Pat. No. 4,285,330, the central core was formed of a pair of concentric cylindrical tubes, the outer tube of which was provided with a plurality of spaced parallel dark strips running lengthwise on the surface of the tube. This construction was not wholly optimal in its design since the light passing between the dark strips had to penetrate both walls of the core, and each had a tendency, because of their cylindrical shape, to reflect the light rather than to absorb its energy.
In U.S. Pat. No. 4,281,641 DeVORE, a core was constructed of a pair of coaxially arranged triangular tubes in which a plurality of fluid conducting conduits were arranged, and on which were attached one or more curved fins for absorbing the sun's energy. The sun's rays had to penetrate a double reflective wall and also had to be absorbed by the fins before being conducted to the fluid conduits.
In U.S. Pat. No. 4,340,035 BEGUN, a core is formed of an outer portion comprising a transparent triangular tube in which is located an inner core member formed as a solid elongated body preferable of metal, having a small axial through conduit for passage of the fluid media and three equally spaced radial projections. The radial projections contact, along their active lengths, the inner edges of the triangular tube so that only separated elongated channels are formed. The inner core body is coated with an absorbing layer, black in nature, so that the sun's light energy is more easily absorbed. On the contrary, however, the rather substantial inner solid core body requires much time to conduct the heat to the fluid media; media flow rate is rather small due to the small diameter of its conduit; thermal flow between the inner and outer core is severely inhibited; and, the cost of manufacture increased by the need to provide an elongated central core body.
Another disadvantage inherent in all of the above collectors is the fact that these units could not be provided in modular form, so that they might be connected in series, to provide ganged collectors of varying desired lengths. As a result, collectors were required to be customized for the space where they would be located. This again contributes to an increase in cost, not generally warranted by the efficiency or productivity of the resultant assembly.
It is the primary object of the present invention to provide a solar collector which provides a more optimal transfer of the sun's energy to a fluid media than those known heretofore, taking into account its simplicity of construction, its use of inexpensive materials and parts and its increased fluid flow rates.
These objects, together with other objects and advantages will be enumerated in detail, as well as be otherwise obvious from the foregoing disclosure of the details of the present invention.